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package net.corda.contracts.asset
import net.corda.contracts.clause.AbstractConserveAmount
import net.corda.contracts.clause.AbstractIssue
import net.corda.contracts.clause.NoZeroSizedOutputs
import net.corda.core.contracts.*
import net.corda.core.contracts.clauses.AnyOf
import net.corda.core.contracts.clauses.GroupClauseVerifier
import net.corda.core.contracts.clauses.verifyClause
import net.corda.core.crypto.CompositeKey
import net.corda.core.crypto.Party
import net.corda.core.crypto.SecureHash
import net.corda.core.crypto.newSecureRandom
import net.corda.core.transactions.TransactionBuilder
import java.util.*
/////////////////////////////////////////////////////////////////////////////////////////////////////////////////////
//
// Commodity
//
// Just a fake program identifier for now. In a real system it could be, for instance, the hash of the program bytecode.
val COMMODITY_PROGRAM_ID = CommodityContract()
/**
* A commodity contract represents an amount of some commodity, tracked on a distributed ledger. The design of this
* contract is intentionally similar to the [Cash] contract, and the same commands (issue, move, exit) apply, the
* differences are in representation of the underlying commodity. Issuer in this context means the party who has the
* commodity, or is otherwise responsible for delivering the commodity on demand, and the deposit reference is use for
* internal accounting by the issuer (it might be, for example, a warehouse and/or location within a warehouse).
*
* This is an early stage example contract used to illustrate non-cash fungible assets, and is likely to change significantly
* in future.
*/
// TODO: Need to think about expiry of commodities, how to require payment of storage costs, etc.
class CommodityContract : OnLedgerAsset() {
/**
* TODO:
* 1) hash should be of the contents, not the URI
* 2) allow the content to be specified at time of instance creation?
*
* Motivation: it's the difference between a state object referencing a programRef, which references a
* legalContractReference and a state object which directly references both. The latter allows the legal wording
* to evolve without requiring code changes. But creates a risk that users create objects governed by a program
* that is inconsistent with the legal contract
*/
override val legalContractReference: SecureHash = SecureHash.sha256("https://www.big-book-of-banking-law.gov/commodity-claims.html")
override val conserveClause: AbstractConserveAmount = Clauses.ConserveAmount()
/**
* The clauses for this contract are essentially:
*
* 1. Group all commodity input and output states in a transaction by issued commodity, and then for each group:
* a. Check there are no zero sized output states in the group, and throw an error if so.
* b. Check for an issuance command, and do standard issuance checks if so, THEN STOP. Otherwise:
* c. Check for a move command (required) and an optional exit command, and that input and output totals are correctly
* conserved (output = input - exit)
*/
interface Clauses {
/**
* Grouping clause to extract input and output states into matched groups and then run a set of clauses over
* each group.
*/
class Group : GroupClauseVerifier>(AnyOf(
NoZeroSizedOutputs(),
Issue(),
ConserveAmount())) {
/**
* Group commodity states by issuance definition (issuer and underlying commodity).
*/
override fun groupStates(tx: TransactionForContract)
= tx.groupStates> { it.amount.token }
}
/**
* Standard issue clause, specialised to match the commodity issue command.
*/
class Issue : AbstractIssue(
sum = { sumCommodities() },
sumOrZero = { sumCommoditiesOrZero(it) }
) {
override val requiredCommands: Set> = setOf(Commands.Issue::class.java)
}
/**
* Standard clause for conserving the amount from input to output.
*/
class ConserveAmount : AbstractConserveAmount()
}
/** A state representing a commodity claim against some party */
data class State(
override val amount: Amount>,
/** There must be a MoveCommand signed by this key to claim the amount */
override val owner: CompositeKey
) : FungibleAsset {
constructor(deposit: PartyAndReference, amount: Amount, owner: CompositeKey)
: this(Amount(amount.quantity, Issued(deposit, amount.token)), owner)
override val contract = COMMODITY_PROGRAM_ID
override val exitKeys = Collections.singleton(owner)
override val participants = listOf(owner)
override fun move(newAmount: Amount>, newOwner: CompositeKey): FungibleAsset
= copy(amount = amount.copy(newAmount.quantity, amount.token), owner = newOwner)
override fun toString() = "Commodity($amount at ${amount.token.issuer} owned by $owner)"
override fun withNewOwner(newOwner: CompositeKey) = Pair(Commands.Move(), copy(owner = newOwner))
}
// Just for grouping
interface Commands : FungibleAsset.Commands {
/**
* A command stating that money has been moved, optionally to fulfil another contract.
*
* @param contractHash the contract this move is for the attention of. Only that contract's verify function
* should take the moved states into account when considering whether it is valid. Typically this will be
* null.
*/
data class Move(override val contractHash: SecureHash? = null) : FungibleAsset.Commands.Move, Commands
/**
* Allows new commodity states to be issued into existence: the nonce ("number used once") ensures the transaction
* has a unique ID even when there are no inputs.
*/
data class Issue(override val nonce: Long = newSecureRandom().nextLong()) : FungibleAsset.Commands.Issue, Commands
/**
* A command stating that money has been withdrawn from the shared ledger and is now accounted for
* in some other way.
*/
data class Exit(override val amount: Amount>) : Commands, FungibleAsset.Commands.Exit
}
override fun verify(tx: TransactionForContract)
= verifyClause(tx, Clauses.Group(), extractCommands(tx.commands))
override fun extractCommands(commands: Collection>): List>
= commands.select()
/**
* Puts together an issuance transaction from the given template, that starts out being owned by the given pubkey.
*/
fun generateIssue(tx: TransactionBuilder, tokenDef: Issued, pennies: Long, owner: CompositeKey, notary: Party)
= generateIssue(tx, Amount(pennies, tokenDef), owner, notary)
/**
* Puts together an issuance transaction for the specified amount that starts out being owned by the given pubkey.
*/
fun generateIssue(tx: TransactionBuilder, amount: Amount>, owner: CompositeKey, notary: Party) {
check(tx.inputStates().isEmpty())
check(tx.outputStates().map { it.data }.sumCashOrNull() == null)
val at = amount.token.issuer
tx.addOutputState(TransactionState(State(amount, owner), notary))
tx.addCommand(generateIssueCommand(), at.party.owningKey)
}
override fun deriveState(txState: TransactionState, amount: Amount>, owner: CompositeKey)
= txState.copy(data = txState.data.copy(amount = amount, owner = owner))
override fun generateExitCommand(amount: Amount>) = Commands.Exit(amount)
override fun generateIssueCommand() = Commands.Issue()
override fun generateMoveCommand() = Commands.Move()
}
/**
* Sums the cash states in the list, throwing an exception if there are none, or if any of the cash
* states cannot be added together (i.e. are different currencies).
*/
fun Iterable.sumCommodities() = filterIsInstance().map { it.amount }.sumOrThrow()
/** Sums the cash states in the list, returning null if there are none. */
@Suppress("unused") fun Iterable.sumCommoditiesOrNull() = filterIsInstance().map { it.amount }.sumOrNull()
/** Sums the cash states in the list, returning zero of the given currency if there are none. */
fun Iterable.sumCommoditiesOrZero(currency: Issued) = filterIsInstance().map { it.amount }.sumOrZero(currency)
